Straw input enhances soil organic carbon stabilization via physical protection and chemical stability

Soil organic carbon (SOC) stability is crucial for the carbon cycle and soil health. While straw input is widely implemented as a carbon sequestration strategy in temperate climate conditions, its impact on SOC stability has not reached a consistent conclusion. Here, a meta-analysis was conducted using data collected from 123 literature sources, comprising 418 paired observations, to analyze SOC accumulation and stability effects of crop straw input and to explore the potential regulatory roles of climate, soil properties, and management factors. Results highlighted that under crop straw input, particulate organic carbon (POC) was the primary driver of SOC accumulation (SOC: 15.6% increase, the ratio of particulate organic carbon to soil organic carbon: 13.3% increase, the ratio of mineral-associated organic carbon to soil organic carbon: 5.2% decrease) and enhanced its stability through physical protection (macroaggregates: 16.4% increase, mean weight diameter: 15.7% increase) and stable chemical structures (decomposition degree: 4.0% increase, humification degree increase). Moreover, key factors affecting SOC accumulation, aggregate stability, and SOC chemical structure stability under crop straw input were identified. Through subgroup analysis, optimal conditions for SOC stability were identified: clay-textured soils with nitrogen (N) application rates of 200-400 kg ha^-1 yr^-1, straw input amounts of 4500-9000 kg ha^-1 yr^-1, and implementation durations greater than 10 years. Given that most field experiments were conducted in temperate regions with straw incorporation by plowing, and that observations were predominantly from China, our findings are primarily applicable to comparable agricultural systems and should be extrapolated to other regions with caution. Nonetheless, they provide critical insights for enhancing SOC sequestration and stability.